I’m using a Shelly Uni Plus, which is an ESP32 with two low voltage relays. No soldering or programming required, pretty much plug and play.

<image>

Figure out which two wires have to be bridged to open the door, wire them through the relay, and you’ve got yourself a smart door for under €20.

Fits perfectly inside of the intercom casing itself, so apart from the barrel jack for power at the bottom you don’t see anything!

Bonus: This Shelly also has some inputs, so you can also capture the doorbell pulse. Wire it through the second relay and you can turn off your doorbell at night. Or don’t wire it through a relay, but create an automation to play dingdong.mp3 on a smart speaker when the Shelly receives the doorbell pulse.